Conveyor apparatus

ABSTRACT

This disclosure pertains to a novel spring biased pusher dog assembly for conveyors. This assembly is disclosed incorporated in an overhead power and free conveyor system, in one embodiment as part of the power line conveyor in which it performs a releasable driving function, and in another embodiment as part of the free line conveyor in which it performs a releasable driven function. The novel assembly is disclosed in a further embodiment performing a driving function as part of a subfloor towline conveyor. There is also disclosed means for rendering the releasable function of the assembly inoperable in those zones of the conveyor where such is desired, as well as means for preventing any driving or driven function at all in any zone desired.

United States Patent 1 Krammer Nov. 27, 1973 CONVEYOR APPARATUS [75 Inventor: Robert Krammer, Farmingto [21] Appl. No.: 150,362

[52] US. Cl...... 104/172 S, 104/172 B, 104/172 ET [5]] Int. Cl B6lb 13/00 [58] Field of Search 104/172 R, 172 B,

104/172 BT, 172 S, 88

[56] References Cited UNITED STATES PATENTS 10/1960 Bishop 1,212,884 3/1966 Germany 104/172 S Primary Examiner-Gerald M. Forlenza Assistant Examiner-Frank E. Werner AttorneyHarness, Dickey & Pierce [5 7 ABSTRACT This disclosure pertains to a novel spring biased pusher dog assembly for conveyors. This assembly is disclosed incorporated in an overhead power and free conveyor system, in one embodiment as part of the power line conveyor in which it performs a releasable driving function, and in another embodiment as part of the free line conveyor in which it performs a releasable driven function. The novel assembly is disclosed in a further embodiment performing a driving function as part of a subfloor towline conveyor. There is also disclosed means for rendering the releasable function of the assembly inoperable in those zones of the conveyor where such is desired, as well as means for preventing any driving or driven function at all in any zone desired.

17 Claims, 14 Drawing Figures PAIENIEUnum 1915 3174.5 5

saw 2 OF 6 l INVENTOR.

PAIENTED Nov 2 7 I975 SHEET 30F 6 PAIENTEDnuvzv I973 SHEET 5 BF 6 id if INVENTOR.

CONVEYOR APPARATUS BACKGROUND AND SUMMARY OF THE INVENTION A power and free conveyor generally comprises a power line conveyor having a track arranged in a loop of some configuration and an endless powered chain to which are connected, either directly or indirectly, pusher elements for driving the load carriers, the latter being supported and guided by a completely separate free line conveyor having a track but no powered chain and arranged generally parallel to and usually below the power line conveyor. The load carriers, or the free line track supported trolleys from which they may be suspended, are provided with driven elements normally positioned in the path of the pusher elements of the power line conveyor, whereby the latter drive the former. In any section of the path of the conveyor where it is desired to cease powering a given carrier, either to accumulate it with other carriers, to avoid a jam or have access to it, or to be free to divert it to a branchline, its driven element or its associated pusher element moves out of its normal path and they disengage. This is generally accomplished without stopping the power line conveyor by either having the path or track of the power line conveyor move away from the path or track of the free line conveyor or vice versa, or by using parallel paths in combination with spring biased pusher elements each of which is capable of being displaced out of engagement with or snapping ofl its driven element when the latter or its associated carrier is physically stopped, either by a special stop or by engagement with other stationary accumulated carriers on the free line conveyor. In the event there is a row of stationary accumulated carriers on the free line conveyor, each spring biased pusher dog will engage and snapp off each driven element on each stationary carrier in succession as the power line conveyor continues its course, often with considerable noise, substantial towing forces and high loads on the stop or accumulated load carriers. Because of the spring release function, conventional spring biased pusher dogs are not normally used to convey loads up inclines.

It is a primary object of the present invention to provide an improved spring biased type pusher dog assem bly.

Another object of the present invention resides in the provision of an improved spring biased type pusher dog on carrier stops and snap off noise are reduced. A related object concerns a provision of such an assembly comprising means whereby snap off pressure may be adjusted and thereby minimized while the assembly is a part of an installed conveyor system.

Another object of the present invention concerns the provision of a conveyor system having means permitting disengagement of the load carriers from the drive means for accumulating or diverting same, and further comprising means for positively preventing such disengagement in zones of the conveyor where disengagement would be undesirable or dangerous, as well as means for positively maintaining disengagement in zones of the conveyor in which it is not desired to drive the carriers, all without having to displace the conveyor tracks themselves. A related object concerns the provision of such means providing positive engagement or positive disengagement which may, if desired, be rendered ineffective in those zones of the conveyor in which it is provided.

A further object of the present invention resides in the provision of an improved spring biased type pusher dog assembly having a pusher dog (driving or driven) of improved configuration to facilitate proper driving engagement not only when it overtakes the element it engages but also when it is overtaken by such element. A related object concerns the provision of such a pusher dog having relatively low friction means for drivingly engaging such element.

Another object of this invention concerns the provision of an improved power and free overhead conveyor system incorporating spring biased driven dog means which is capable of carrying mixed loads on respective load carriers with reduced towing forces and which is less expensive in applications where more drive dogs are utilized than load carriers.

Another object of the present invention resides in the provision of a subfloor towline conveyor system for conventional tow trucks, which uses spring biased rather than rigid pusher dog assemblies on the towline, whereby safety is enhanced and the need for providing expensive bumper release mechanisms on the tow trucks is obviated in many applications.

These and other objects, features and advantages of the present invention will become apparent from the subsequent description and the appended claims, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. l is an elevational view of a portion of a power and free conveyor system embodying tthe principles of the present invention, with certain parts broken away;

FIG. 2 is a sectional view taken along line 2-2 in FIG. 1;

FIG. 3 is an enlarged elevational view of the spring biased pusher dog assembly shown in FIG. 1, with the front plate thereof broken away;

FIG; 4 is a sectional view taken along line 4-4 in FIG. 3;

FIG. 5 is a sectional view taken along line 5-5 in FIG. 3;

FIG. 6 is an elevational view of a modified spring biased pusher dog assembly incorporating the principles of the present invention, with certain parts broken away;

. FIG. 7 is a partial bottom view of the assembly shown in FIG. 6;

FIG. 8 is an elevational view of an alternative way of mounting the spring biased pusher dog assembly of the present invention on a power and free conveyor, with certain parts broken away;

FIG. 9 is a sectional view taken along line 9-9 in FIG. 8;

FIG. 10 is an elevational view of a portionof a modified form of an overhead power and free conveyor embodying the principles of the present invention, with certain parts broken away;

FIG. 11 is a partial sectional view looking along the line Ill-ll in FIG. 10;

FIG. 12 is an elevational view of a portion of a subfloor towline conveyor incorporating the principles of the present invention, with certain parts broken away;

FIG. 13 is a sectional view taken along line 13-13 in FIG. 12; and

FIG. 14 is a partial pictorial view illustrating one feature of the present invention.

Referring more particularly to the drawings, it is shown in FIGS. 1 and 2 a power and free conveyor system comprising a power line conveyor indicated generally at and a conventional free line conveyor indicated generally at 1 1. Power line conveyor 10, of which only a portion is shown, may extend for any length desired, usually in an endless loop of some configuration, and comprises a support and guide rail or track 12 on which are carried a plurality of conventional powered trolleys indicated generally at 14 which are connected to a conventional conveyor chain 16, such as the rivetless chain shown. Supported by chain 16 are a plurality of spaced spring biased pusher dog assemblies, one of which is indicated generally at 17. Each trolley 14 comprises a pair of brackets 18 each having rotatably mounted to the upper end a wheel 20. The trolley 14 is assembled in the manner shown in FIG. 2 with wheels 20 riding on the lower flanges of rail 12, respectively, and with the lower ends of the brackets inserted within the center of a link 22 of chain 16, the brackets being provided with notches 24 adapted to mechanically interlock with link 22, the interlock being maintained by the provision of a spacer 26 between the lower ends of the bracket and the entire assembly being held together by threaded fasteners or the like 28. For maximum support, a trolley 14 is provided on each of the chain links 22 immediately adjacent each pusher dog assembly 17, and if necessary additional trolleys 14 may be provided between assemblies 17, as is known in the art.

Free line conveyor 11 comprises a pair of opposed channel shaped guide and support rails or tracks 30 extending generally parallel to and beneath rail 12. Rails 30 are supported by a plurality of spaced brackets 32 affixed to rail 12, one of which is shown in FIGS. 1 and 2, and rollably supported by rails 30 are a plurality of load carriers or load carrying trolleys 34, one of which is shown. Each trolley 34 comprises a body member 36 to which are rotatably mounted four wheels 38 adapted to ride within rails 30. The upper end of member 36 is provided with a driver lug 40 and adjacent the lower end is a pair of rotatably mounted rollers 42 adapted to engage the lower edges 44 of rails 30 to restrict movement of the trolley transversely to the longitudinal axis of rails 30. Each roller 42 is disposed within a slot 46 in member 36 and is mounted for rotation about a vertically arranged pin 48 retained in a vertical bore 50 by means of a set screw 52.

Affixed to the lower edge of member 36, as by threaded fasteners 54, are a pair of angle brackets 56 to which is rigidly secured a longitudinally extending bumper assembly 58, to the opposite ends of which (only one end being shown in FIG. 1) are affixed conventional bumper plates 60. Afiixed to bumper assembly 58 beneath brackets 56, as by threaded fasteners 62, is a load supporting element 64 having an aperture 66 therethrough for attachment and support of whatever load is to be carried by the free line conveyor. Assembly 58 is slightly greater in longitudinal length than the load so that when the free line trolleys are accumulated bumper plates 60 will engage one another prior to the loads hitting one another.

As best seen in FIGS. 3, 4 and 5, pusher dog assembly 17 comprises an inverted U-shaped body member 68 in which is pivotally mounted, by means of a pivot pin 70 extending transversely therethrough, a pusher dog 72.

Also pivotally mounted within body member 68, as by means of a pin 74 extending transversely therethrough, is a hold back dog 76 having at one end a free line trolley engaging surface 78 and at the opposite end a projection 80 adapted to engage, under the influence of gravity, a pin 82 extending transversely through body member 68, the latter pin maintaining the drive dog in its normal operating attitude, as shown in FIGS. 1 and 3. On the outer surface of each side of body member 68 there is disposed a plate 84 having suitably located apertures for receiving pins 74 and 82 therethrough. As best seen in FIG. 4, the outer ends of pins 74 and 82 are held in place by means of conventional snap rings 86 cooperating with appropriate grooves in the pins. Pin

70 is of a length substantially equal to the width of body member 68 and plates 84 partially overlie pin 70 to retain the latter in place, thereby providing the upper portion of both sides of body member 68 with a substantially flush surface. It has been found desirable to provide such a flat surface for clearing and/or rollingly engaging the conventionally utilized roller turn rollers or traction wheel normally found at turns on conveyors of the present type.

Pusher dog assembly 17 is affixed directly to and forms a part, of the link of the conveyor chain positioned between the links thereof supported by trolleys 14. As best seen in FIGS. 1 and 3, assembly 17 is so affixed .to chain 16 by means of master pins 90, the upper bight portion of body member 68 forming the upper half of the link and conventional link element 88 forming the lower half. This is accomplished by providing bight portion 91 with a pair of apertures of the same pitch as chain 16 and inserting upwardly through these apertures, the holes in the ends of the adjacent links of chain 16 and link element 88, master pins which are held in place by nuts 92, the heads 94 of the master pins 90 actually holding the assembly in place and maintaining it as an integral part of that link of the conveyor chain.

As best seen in FIGS. 1 and 3, the free end of pusher dog 72 which projects away from body member 68 (from a direction opposite to the direction of normal movement of the conveyor) is provided with a bifurcated enlarged portion 96 having a generally rearwardly and downwardly facing convex curved surface 98 and a generally forwardly and downwardly facing concave curved surface 100. Between surfaces 98 and 100 and the legs of bifurcated portion 96 is rotatably mounted, as by means of a pin 102 held in place by conventional snap rings 101, a roller 104 adapted to drivingly engage lug 40 on the free line trolley. As can be seen, roller 104 is normally in horizontal alignment with surface 78 on hold back dog 76 and driving lug 40.

The opposite end of pusher dog 72, indicated at 106, engages on the lower surface thereof a compression spring 108, the opposite end of which rests on a generally U-shaped support member permanently affixed between the legs of body member 68. Spring 108 thus resiliently biases pusher dog 72 in a counterclockwise direction as shown, i.e., biases roller 104 downwardly. The lowermost position of roller 104, as well as the precompression of spring 108, is determined by a generally vertically disposed set screw 112 threadably engaging end portion 106 and engaging at its free end the lower surface of head 94 of one of the master pins. Threaded adjustment of screw 112, through a suitable aperture 114 in member 110, provides fine adjustments to the precompression of spring 108 and establishes the degree of counterclockwise movement of pusher dog 72 as can be easily visualized. Screw 112 also helps retain spring 108 in place. Coarser adjustments in the spring precompression are made by changing to springs of different rates and/or by adding washers or spaces beneath tthe spring.

As can be visualized, when assembly 17 overtakes a lug 40, hold back dog 76 merely swings up and out of the way to permit lug 40 to engage roller 104. Hold back dog 76 then drops back to the position shown and roller 104, which is being moved in the direction indicated by the power line conveyor, pushes lug 40 and its load along the free line conveyor. If lug 40 should for some reason he a little high, concave surface 100 on pusher dog 72 will either smoothly push it down or cause dog 72 to raise so that roller 104 will be in a proper driving position. Driving engagement might also occur by a load carrier and its lug 40 overtaking a pusher dog 72, in which case the engagement of lug 40 and surface 98 will cause pusher dog 72 to smoothly raise and permit lug 40 to move into the space between it and hold back dog 76, after which normal driving engagement will occur. Surfaces 98 and 100 are designed to prevent a jam up by assuring that all forces likely to be encountered by the free end of pusher dog 72 tend to rotate it, rather than push it against its pivot pin. Should tthe load carrier ever tend to accelerate ahead of assembly 17, as on a downhill incline, hold back dog 76 will prevent lug 40 from becoming disengaged from assembly 17. Whenever a load carrier is physically stopped or restrained, either intentionally or unintentionally, roller 104 will roll up the railing surface of lug 40 against the bias of spring 108 until it snaps ofi of the lug, after which no driving forces will be exerted on the lug until the next assembly 17 comes along. The resistance to snap off, and hence the maximum towing force exerted on a carrier without release or snap off is govemed by the precompression and spring rate of spring 108. In the present assembly such force may be easily varied or adjusted in the manner discussed,and in most applications the snap off force should be slightly greater than the force necessary to tow the heaviest load anticipated up the greatest incline or against the greatest resistance anticipated, in any zone in which snap olT is permitted.

Adjacent the free end of pusher dog 72 there is provided an outwardly extending boss 116 on each side thereof. Bosses 116 are adapted to cooperate with a third rail 118 FIG. 2) extending generally parallel to the path of the conveyor and located adjacent the path of movement one or the other of bosses 116, in those zones of the conveyor where it is desired to change the function of pusher dog 72 from one having a spring bias dog to one which is fixed. Thus, at any zone of the conveyor where it is desired to maintain all of pusher dogs 72 in a positive driving relationship with respect to free line conveyor 11, a third rail 118 should be provided for the length of that zone disposed slightly above bosses 116, as shown in FIG. 2. Thus, any tendency of any pusher dog 72 to release or move upwardly out of driving engagement with its lug 40 is positively prevented by engagement of its boss 116 with third rail 118. The use of a third rail in this manner might be desirable in zones in which the conveyor is disposed on an upward incline, in order to prevent release of the pusher dogs 72 under the increased influence of the gravity forces acting on the load, in zones in which loads are being conveyed through a furnace or the like and it is important to prevent any release or accumulation of free line trolleys and their loads therein Use on inclines may reduce towing forces because springs 108 can be set at lower precompression settings since they do not have to overcome the tendency to release under the influence of large loads moving up an incline. In zones of the conveyor in which it is desired to maintain pusher dogs 72 out of driving engagement with the free line trolley, third rail 116 may be provided with a suitable ramp at the entrance end to cam bosses 116 and hence pusher dogs 72 up to a level at which no driving engagement will be made with the free line trolleys. Such a zone might be used in a switching zone, or where it is desired to accumulate the load carriers. In FIG. 14 there is pictorially illustrated a third raj] 118 having a movable or pivotal ramp 1 19. When ramp ll 19 is horizontal bosses 1116 pass under the ramp, either in a normal mode if rail 118 is high enough to permit snap off or in a positive drive mode if it is not. When ramp 119 is lowered to the position shown in plantorn lines,

by any suitable mechanism, bosses 1 16 will be cammed upwardly and carried along the top of rail 119 so that pusher dogs 72 will be positively but selectively maintained out of driving engagement with lugs 4M). Load carrier accumulation in this manner, rather than by snap off, significantly reduces towing forces, loads on the carrier stops, and noise. Hold up or hold down rails 11%, with or without a ramp, may be provided on either or both sides of the conveyor, two oppositely projecting bosses 116 being provided on each pusher dog 72. If it is found in a given application that there is excessive friction generated between rail 1 18 and bosses 116, the latter may be provided with suitable rollers. If desired, rail us may be mounted so that the entire rail, or a section thereof, may be swung out of the way of bosses 116 in order to provide selectively operable positive zones.

Another preferred embodiment of the spring loaded pusher dog assembly, onethat is particularly suited for heavy duty applications, is shown in FIGS. 6 and 7, the same reference numerals being used to designate parts identical to those previously described. In this embodiment the pusher dog assembly, indicatedgenerally at 17, comprises a body member M0 generally U-shaped in cross-section and having both sides thereof cut away at the forward edges thereof, as at 3 02. Dogs 72 and 76 are secured to body member 3% by means of pins and 74 in the same way as in the previous embodiment. The difference in this embodiment resides in the means for supporting spring 10%, which means comprises a pair of spaced plates 3% interconnected at their forward ends by means of a cup-shaped element M6 in which'is positioned compression spring 10$, cup ele ment 3% being provided with an adjusting aperture" 30% to facilitate adjustment in exactly the same manner as in the previous embodiment. Plates 304 engage the sides of body portion 3MP and are held in place by means of pins 74 and b2 which extend therethrough and are provided at their outer ends with suitable snap rings or the like, as in the previous embodiment. One of the primary advantages of the construction of this embodiment resides in the manner in which it facilitates assembly of the device, particularly where exceedingly high rate springs 10% are used, as well as spring changes. In such a situation the plates 3% and hence cup element 306 are initially assembled to body member 300 solely by pin 74, which also serves as a pivot for hold back dog 76. The cup element 306 is then free to swing from body member 300 to permit insertion of spring 108, and thereafter may be urged against the remainder of the assembly and pin 82 inserted to lock it in place and also provide a stop for the downward movement of hold back dog 76, pin 82 providing a dual function. This is much easier than trying to compress spring 108 and then inserting it into an already assembled device. It also provides means for conveniently inserting washers or the like under spring 108 should such be desired to increase the precompression thereof. Spring changes on a fully installed conveyor are similarly facilitated. Plates 304 also serve the function of holding pin 70 in place, as did plates 84 in the previous embodiment. Assembly 17 operated in exactly the same manner as assembly 17.

A variation of the embodiment of this invention discussed above is shown in FIGS. 8 and 9. This variation differs only in the manner in which the pusher dog assembly is mounted to the power line conveyor, like reference numerals being used to designate like parts. In applications where a relatively light power line conveyor chain is used, or the chain is of relatively short pitch or if particularly heavy loads or towing forces are to be encountered, it may be desirable to mount each pusher dog assembly 17 to a load bar extending over several pitches of the chain, rather than to a single link thereof. One way in which this may be accomplished, utilizing trolleys 14, is shown in FIGS. 8 and 9. Trolleys 14, which may be suspended from and driven by any conventional power line conveyor or driving means are each provided at the lower end thereof with a downwardly extending projection 200 having at the lower end a T-attachment in the form of a transversely extending flange 202. Assembly 17, instead of being connected directly to the conveyor chain, is rigidly connected by any suitable means to a load bar 204 having a longitudinally extending slot 206 at each end thereof. Disposed in respective slots 206 of load bar 204 are projections 200 of adjacent trolleys 14. Projections 200 and flanges 202 are each of a width less than the width of each slot 206 so that they may be inserted therethrough, rotated 90 to the position shown and affixed to the power line conveyor. Trolleys 14 are each provided with an enlarged portion 208 to prevent load bar 204 from moving upwardly thereon, the latter being normally supported by flanges 202. By virtue of this arrangement, each pusher dog assembly 17 is suspended directly from the power line track through the trolleys, rather than from the conveyor chain. Operation and adjustment of the assembly is the same as previously described, although the end of adjusting screw 1 12 (not shown) will engage the bight portion of body member 68 rather than the head of master pin.

In FIGS. 10 and 11 there is shown a modified power and free conveyor system in which each pusher dog assembly, one of which is shown at 17", is utilized in an inverted fashion. In this embodiment, the power line conveyor is identical to that described in the first embodiment, as are power line trolleys 14 and conveyor chain 16, the only difference residing in the provision of a driving lug 400 forming a part of the lower half of the conveyor link disposed between adjacent trollies 14, in lieu of pusher dog assembly 17 which formed that half of that link in the first embodiment. Driving lug 400 is secured to conveyor chain 16 in the conventional manner utilizing master pins having heads 94 and is locked in place by means of nuts 92. If desired, it could alternatively be secured to a load bar, such as shown in FIG. 8, or even directly to the bottom of a trolley 14. Free line trolley 11 is identical in construction to that described in connection with the first embodiment, with the exception that instead of a driving lug 40 at the upper end thereof, there is mounted, as by welding or suitable threaded fasteners, bight portion 91 of body member 68 of pusher dog assembly 17", the latter being mounted in an inverted attitude with respect to the first embodiment, as best seen in FIG. 10. Pusher dog assembly 17" is identical to pusher dog assembly 17 except for inverted operation there is provided a spring 402 to urge hold back dog 76 into its operative position, as shown, against the influence of gravity. Spring ,402 may be located anywhere so long as it provides a sufficient upward force to hold the dog 76 in the position sought; for example, it may be inserted between opposed recesses in dogs 72 and 76 in the manner shown in FIG. 11. Because the tension of spring 402 will be considerably less than that of spring 108 the reaction force of such an arrangement on arm 72 will be negligible. Dog 76 can alternatively be weighted at its inner end so that gravity will maintain it in its operative position shown. The interaction between dog 72 and lug 400 and between dog 76 and lug 400 (including snap off, hold back, etc.) is exactly the same as that described in the first embodiment with respect to corresponding lug 40, except that lug 40 is powered and assembly 17 is not. Assembly 17" adjusts in the same manner as assembly 17, except that the end of screw 1 12 engages the bight portion of body member 68, rather than the head of a master pin. The embodiment of FIGS. 10 and 11 is particularly suited to applications where mixed loads are intended to be carried by the conveyor system, i.e. one free line trolley might be supporting a very heavy load, the next one a very light load, etc., a relatively common practice in manufacturing and assembly plants. In such applications spring 108 for each pusher dog assembly may be of such a rate or so adjusted to be just strong enough to prevent unintentional release of the particular load intended to be carried by the attached free line trolley. By requiring a spring no stiffer than that required for a particular load, overall conveyor power requirements are decreased, the noise which accompanies snap off is reduced in magnitude, and loads on carrier stops are reduced. In the first embodiment each pusher dog had to be provided with a spring of sufficient stiffness to accommodate the heaviest load to be carried by the conveyor, and therefore it is more suitable for conveyor systems adapted to handle relatively unifonn loads or random mixed loads or unknown loads. Another advantage of the embodiment shown in FIGS. 10 and 11 occurs in installations in which there are considerably more driving lugs than there are free line trolleys, because each drive lug of this embodiment is considerably less expensive than a spring pusher dog assembly which would otherwise be required. A third rail 118 may be used in this system in exactly the same manner previously described, one being shown in phantom in FIGS. 10 and 11 for maintaining pusher dog 72 in positive driven engagement.

In FIGS. 12 and 13 there is shown a subfloor towline conveyor system also embodying the principles of the present invention. The overall construction of the towline is conventional, comprising a longitudinally extending trough in the floor 500 extending over the entire path of the conveyor, usually a closed loop, in which is disposed a pair of opposed channel shaped track elements 502, a channel shaped shield member 504 and a pair of top plates 506 flush with the floor and defining therebetween a longitudinally extending slot 508 through which a conventional tow pin 510 of a common tow truck may be dropped for driving engagement by the tow line conveyor. Disposed within the trough defined by the aforesaid elements is a conventional conveyor chain 512, which is shown as being of the rivetless type. Secured to chain 512 are a plurality of spring biased pusher dog assemblies, one of which is shown in 17". Assembly 17" is connected to the chain 512 in exactly the same manner as in the embodiment of FIG. 1 except that the bight portion 92 of body member 68 is provided at each end with an extension 516 through which is provided a suitable aperture through which extends a master pin 90. To hold the assembly and chain together, the pusher dog assembly forms one half of one of the links of the conveyor chain, as in proceeding embodiments. Spring biased pusher dog 17" is identical in construction, adjustment and operation to assembly 17" illustrated in FIG. 10, except for the provision of extensions 516 and a downwardly extending projection 517 which carries oppositely projecting bosses 116.

Spring biased pusher dog assembly 17" and conveyor chain 512 connected thereto are supported by means of a plurality of wheels 518 guided and supported in track elements 502, the pair of wheels 518 on each side of assembly 17 being rotatably connected to a bracket 520 which is afiixed, by welding or the like, to the side of body member 68. Brackets 520 on each assembly 17" serve to hold pins 74, 70 and 82 in place in the same manner as pin 70 was in the previous embodiments. Additional trolleys of conventional configuration may be supported and guided by track ele ments 502 to provide support for conveyor chain 512 between assemblies 17".

The load carriers for the present subfloor conveyor can be conventional wheeled tow trucks (not shown) having at the forward end thereof a vertically displaceable tow pin, the bottom end of which is indicated at 510. When it is desired to attach a tow truck to the subfloor conveyor, the truck is wheeled over to the conveyor and tow pin 510 is dropped through slot 508, whereby it will be engaged by the next driving element (roller 104) to arrive on the continuously operating subfloor tow line. The tow pin and hence tow truck are pushed over the course of the conveyor until such time as the pin is raised out of engagement with assembly 17", or the tow truck encounters a stop or other obstacle which will cause pusher dog 72 to snap off the tow pin in the usual manner. Truck accumulation is accomplished in this manner. On downward inclines hold back dog 76 prevents the tow truck from accelerating ahead of assembly 17". One advantage of the present arrangement over a conventional tow line system in which a rigid drive is provided and in which the tow pin is connected to a bumper on the truck which raises the tow pin when it encounters an obstacle, is that with the present arrangement the drive dog will release regardless of the obstacle encountered and the manner in which it is encountered, whereas in the conventional system to obstacle has to be more or less ahead by the bumper for the tow pin to release. The present arrangement is therefore safer, and obviates the need for relatively expensive accumulating bumpers in certain applications.

The subfloor towline embodiment of FIGS. 12 and 13 is also adapted to use the aforedescribed third rail principle in those zones of the conveyor system in which it is desired either to maintain positive driving engagement or positive disengagement. In such zones a longitudinally extending third rail 522 may be provided secured to one or the other of track elements 502 by means of a plurality of spaced mounting elements 524. Rail 522 functions in exactly the same manner as previously described rail 1118 and is disposed in the same relationship to bosses 116 as rail 11% is in the preceding embodiments. As shown in FIGS. 12 and 13, rail 522 is positioned for a positive drive mode of operation.

If desired, spring biased pusher dog assembly 17" may be mounted on its side to the side of the conveyor chain in those applications in which a low profile is important. Furthermore, assembly 117" is also ideally suited for use with sliding tow line chains, or for that matter any conventionally used chain.

Thus, there is disclosed in the above description and in the drawings several embodiments of the invention which fully and effectively accomplish the objects thereof. However, it will be apparent that other variations in the details of construction may be indulged in without departing from the sphere of the invention herein described, or the scope of the appended claims.

What is claimed is:

l. A conveyor comprising: powered driving means including a plurality of spaced driving units propelled along the course of the conveyor; a plurality of carrier means movable along a path generally parallel and adjacent to the path of said driving units for carrying a load; driven means rigidly connected to each said carrier means; first lever means movably connected to each said driving unit for drivingly engaging said driven means on one of said carrier means to drive said carrier means; release means on each said driving unit for permitting disengagement of its associated first lever means from the driven means of the carrier means driven thereby in response to a physical restraint being imposed against movement of such driven carrier means along said path; second lever means movably connected to each said driving unit in a leading relationship with respect to said first lever means on the same said unit, said second lever means being operable to prevent a carrier means from moving forwardly past a driving unit while permitting a driving unit to move forwardly past a carrier means; and means disposed along a zone of the course of the conveyor for rendering each said release means inoperable in said zone.

2. A conveyor as claimed in claim ll, wherein said first levers extend from said units in a direction substantially opposite from the direction of movement of said units.

3. A conveyor comprising: powered driving means including a plurality of spaced driving lugs propelled along the course of the conveyor; a plurality of carrier means movable along a path generally parallel and adjacent to the path of said driving units for carrying a load; a driving unit connected to each said carrier means; first lever means movably connected to each said driving unit for drivingly engaging one of said driving lugs to drive said carrier means; release means on each driving unit for permitting disengagement of its associated first lever means from its driving lug in response to a physical restraint being imposed against movement of its carrier means along said path; second lever means movably connected to each said driving unit in a trailing relationship with respect to said first lever means on the same said unit, said second lever means being operable to prevent a carrier means from moving forwardly past a driving unit while permitting a driving unit to move forwardly past a carrier means; and means disposed along a zone of the course of the conveyor for rendering each said release means inoperable in said zone.

4. A conveyor as claimed in claim 3, wherein said first levers extend from said units substantially in the direction of movement thereof.

5. A conveyor as claimed in claim 1, wherein said means for rendering said release means inoperable comprises means for maintaining said first lever means in driving engagement with its driving lug during the course of said zone.

6. A conveyor as claimed in claim 1, wherein said means for rendering said release means inoperably comprises means for moving said first lever means out of engagement with its driving lug and maintaining it out of such engagement during the course of said zone.

7. A conveyor as claimed in claim 3, wherein said means for rendering said release means inoperable comprises means for maintaining said first lever means in driving engagement with its driving lug during the course of said zone.

8. A conveyor as claimed in claim 3, wherein said means for rendering said release means inoperable comprises means for moving said first lever means out of engagement with its driving lug and maintaining it out of such engagement during the course of said zone.

9. A conveyor comprising: a powered driving element; a driven element adapted to carry a load, said elements being mounted for longitudinal movement along generally parallel paths along the course of the conveyor; a lug connected to one of said elements and having a first drive surface; an arm pivotally connected to the other of said elements, said arm projecting away from said other element in a generally longitudinal and slightly transverse direction and having a second drive surface thereon adapted to engage said first drive surface to transmit power from said powered driving element to said driven element, said second drive surface being the cylindrical outer surface of a roller rotatably mounted on said arm, said first drive surface of said lug being positioned between said second drive surface and the pivotal axis of said arm when said drive surfaces engage one another; spring means biasing said arm to a position in which such driving engagement will occur, said spring means being arranged to yield in response to driving forces in excess of a given magnitude to permit said arm to pivot out of engagement with said lug; and means defining a cam surface on the free end of said arm beyond said second drive surface to cause said arm to pivot away from said lug when the latter engages the free end of said arm.

10. A conveyor as claimed in claim 9, wherein the trailing and leading surfaces of said lug are generally flat and lie in planes substantially perpendicular to the path of movement thereof.

11. A conveyor comprising: a powered driving element; a driven element adapted to carry a load, said elements being mounted for longitudinal movement along generally parallel paths along the course of the conveyor; a lug connected to one of said elements and having a first drive surface; an arm pivotally connected to the other of said elements, said arm projecting away from said other element in a generally longitudinal and slightly transverse direction and having a second drive surface thereon adapted to drivingly engage said first drive surface to transmit power from said powered driving element to said driven element, said first drive surface of said lug being positioned between said second drive surface and the pivotal axis of said arm when said drive surfaces drivingly engage one another; spring means biasing said arm to a position in which such driving engagement will occur, said spring means being arranged to yield in response to driving forces in excess of a given magnitude to permit said arm to pivot out of engagement with said lug; a cam follower surface on said arm; and a cam disposed along a portion of the path of said arm adapted to engage said follower surface for physically controlling the position of said arm with respect to said lug; and a hold back dog pivotally connected to said other element, said hold back dog having a stop surface thereon normally facing said second drive surface and being longitudinally spaced therefrom.

12. A conveyor comprising: a powered driving element; a driven element adapted to carry a load, said elements being mounted for longitudinal movement along generally parallel paths along the course of the conveyor; a lug connected to one of said elements and having a first drive surface; an arm pivotally connected to the other of said elements, said arm projecting away from said other element in a generally longitudinal and slightly transverse direction and having a second drive surface thereon adapted to drivingly engage said first drive surface to transmit power. from said powered driving element to said driven element, said arm projecting in a generally leading direction with respect to said other element, said first drive surface of said lug being positioned between said second drive surface and the pivotal axis of said arm when said drive surfaces drivingly engage one another; spring means biasing said arm to a position in which such driving engagement will occur, said spring means being arranged to yield in response to driving forces in excess of a given magnitude to permit said arm to pivot out of engagement with said lug; a cam follower surface on said am; and a cam disposed along a portion of the path of said arm adapted to engage said follower surface for physically controlling the position of said arm with respect to said lug.

13. A conveyor as claimed in claim 9, wherein said arm and spring means are mounted on said powered driving element and said lug is mounted on said driven element.

14. A conveyor as claimed in claim 9, wherein said arm and spring means are mounted on said driven element and said lug is mounted on said powered driving element.

15. A conveyor as claimed in claim 9, wherein said lug is rigidly mounted to said one element.

16. A conveyor as claimed in claim 9, wherein said arm is mounted so that driving forces exerted thereon will tend to pivot it out of driving engagement with said lug.

17. A conveyor as claimed in claim 9, further comprising adjusting means for adjusting the biasing force of said spring means and the transverse position of said second driving surface.

t f k '8 l UNITED STATES PATENT oFFIcE CERTIFICATE OF CRRECTWN Patent O- 3, 774,546 Dated November 27,, 1973 Inventorfli) Robert Krammer It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 36, 'snapp" should be snap Column 2, line 34, 'tthe" should be the Column 3, line 42, "driver" should be driving Column 5, line 7, "tthe should be the Column 5, line 28, "tthe" should be the Column 5, line 33, "railing" should be trailing Column 5, line43, after "be" insert just Column 9, line 18, "92" should be 91 Column 10, line 1, "to" should be the Column 11, line 2, after "each insert said Signed and sealed this 23rd day of April 1971 (SEAL) Attes t2 EDlAiARD I LFLETCHERN'RW (3., MARSHALL DANN Attesting Officer Commissioner of Patents FORM PO-IOSO (10-69) v usco -gc 59 75.;25 1 us GOVERNMENT PRINTING OFFICE: I969 0-366-334 

1. A conveyor comprising: powered driving means including a plurality of spaced driving units propelled along the course of the conveyor; a plurality of carrier means movable along a path generally parallel and adjacent to the path of said driving units for carrying a load; driven means rigidly connected to each said carrier means; first lever means movably connected to each said driving unit for drivingly engaging said driven means on one of said carrier means to drive said carrier means; release means on each said driving unit for permitting disengagement of its associated first lever means from the driven means of the carrier means driven thereby in response to a physical restraint being imposed against movement of such driven carrier means along said path; second lever means movably connected to each said driving unit in a leading relationship with respect to said first lever means on the same said unit, said second lever means being operable to prevent a carrier means from moving forwardly past a driving unit while permitting a driving unit to move forwardly past a carrier means; and means disposed along a zone of the course of the conveyor for rendering each said release means inoperable in said zone.
 2. A conveyor as claimed in claim 1, wherein said first levers extend from said units in a direction substantially opposite from the direction of movement of said units.
 3. A conveyor comprising: powered driving means including a plurality of spaced driving lugs propelled along the course of the conveyor; a plurality of carrier means movable along a path generally parallel and adjacent to the path of said driving units for carrying a load; a driving unit connected to each said carrier means; first lever means movably connected to each said driving unit for drivingly engaging one of said driving lugs to drive said carrier means; release means on each driving unit for permitting disengagement of its associated first lever means from its driving lug in response to a physical restraint being imposed against movement of its carrier means along said path; second lever means movably connected to each said driving unit in a trailing relationship with respect to said first lever means on the same said unit, said second lever means being operable to prevent a carrier means from moving forwardly past a driving unit while permitting a driving unit to move forwardly past a carrier means; and means disposed along a zone of the course of the conveyor for rendering each said release means inoperable in said zone.
 4. A conveyor as claimed in claim 3, wherein said first levers extend from said units substantially in the direction of movement thereof.
 5. A conveyor as claimed in claim 1, wherein said means for rendering said release means inoperable comprises means for maintaining said first lever means in driving engagement with its driving lug during the course of said zone.
 6. A conveyor as claimed in claim 1, wherein said means for rendering said release means inoperably comprises means for moving said first lever means out of engagement with its driving lug and maintaining it out of such engagement during the course of said zone.
 7. A conveyor as claimed in claim 3, wherein said means for rendering said release means inoperable comprises means for maintaining said first lever means in driving engagement with its driving lug during the course of said zone.
 8. A conveyor as claimed in claim 3, wherein said means for rendering said release means inoperable comprises means for moving said first lever means out of engagement with its driving lug and maintaining it out of such engagement during the course of said zone.
 9. A conveyor comprising: a powered driving element; a driven element adapted to carry a load, said elements being mounted for longitudinal movement along generally parallel paths along the course of the conveyor; a lug connected to one of said elements and having a first drive surface; an arm pivotally connected to the other of said elements, said arm projecting away from said other element in a generally longitudinal and slightly transverse direction and having a second drive surface thereon adapted to engage said first drive surface to transmit power from said powered driving element to said driven element, said second drive surface being the cylindrical outer surface of a roller rotatably mounted on said arm, said first drive surface of said lug being positioned between said second drive surface and the pivotal axis of said arm when said drive surfaces engage one another; spring means biasing said arm to a position in which such driving engagement will occur, said spring means being arranged to yield in response to driving forces in excess of a given magnitude to permit said arm to pivot out of engagement with said lug; and means defining a cam surface on the free end of said arm beyond said second drive surface to cause said arm to pivot away from said lug when the latter engages the free end of said arm.
 10. A conveyor as claimed in claim 9, wherein the trailing and leading surfaces of said lug are generally flat and lie in planes substantially perpendicular to the path of movement thereof.
 11. A conveyor comprising: a powered driving element; a driven element adapted to carry a load, said elements being mounted for longitudinal movement along generally parallel paths along the course of the conveyor; a lug connected to one of said elements and having a first drive surface; an arm pivotally connected to the other of said elements, said Arm projecting away from said other element in a generally longitudinal and slightly transverse direction and having a second drive surface thereon adapted to drivingly engage said first drive surface to transmit power from said powered driving element to said driven element, said first drive surface of said lug being positioned between said second drive surface and the pivotal axis of said arm when said drive surfaces drivingly engage one another; spring means biasing said arm to a position in which such driving engagement will occur, said spring means being arranged to yield in response to driving forces in excess of a given magnitude to permit said arm to pivot out of engagement with said lug; a cam follower surface on said arm; and a cam disposed along a portion of the path of said arm adapted to engage said follower surface for physically controlling the position of said arm with respect to said lug; and a hold back dog pivotally connected to said other element, said hold back dog having a stop surface thereon normally facing said second drive surface and being longitudinally spaced therefrom.
 12. A conveyor comprising: a powered driving element; a driven element adapted to carry a load, said elements being mounted for longitudinal movement along generally parallel paths along the course of the conveyor; a lug connected to one of said elements and having a first drive surface; an arm pivotally connected to the other of said elements, said arm projecting away from said other element in a generally longitudinal and slightly transverse direction and having a second drive surface thereon adapted to drivingly engage said first drive surface to transmit power from said powered driving element to said driven element, said arm projecting in a generally leading direction with respect to said other element, said first drive surface of said lug being positioned between said second drive surface and the pivotal axis of said arm when said drive surfaces drivingly engage one another; spring means biasing said arm to a position in which such driving engagement will occur, said spring means being arranged to yield in response to driving forces in excess of a given magnitude to permit said arm to pivot out of engagement with said lug; a cam follower surface on said arm; and a cam disposed along a portion of the path of said arm adapted to engage said follower surface for physically controlling the position of said arm with respect to said lug.
 13. A conveyor as claimed in claim 9, wherein said arm and spring means are mounted on said powered driving element and said lug is mounted on said driven element.
 14. A conveyor as claimed in claim 9, wherein said arm and spring means are mounted on said driven element and said lug is mounted on said powered driving element.
 15. A conveyor as claimed in claim 9, wherein said lug is rigidly mounted to said one element.
 16. A conveyor as claimed in claim 9, wherein said arm is mounted so that driving forces exerted thereon will tend to pivot it out of driving engagement with said lug.
 17. A conveyor as claimed in claim 9, further comprising adjusting means for adjusting the biasing force of said spring means and the transverse position of said second driving surface. 